The proposed research evaluates a potentially useful animal model of the acquisition of adaptive motor behavior in socially living individuals. The focus is on the acquisition of manipulative behavior in infant tufted capuchin monkeys (Cebus apella). The work builds upon the principal investigator's previous observations of the development of tool-using and simple tool-making in a breeding group of capuchins, including infants. The unique repertoire of these particular monkeys affords an opportunity to study the ontogeny of manipulative behaviors culminating in tool use in socially-reared monkeys. Observations of the manipulative activity of immature capuchins (newborn to four years) will provide data on the timing and sequence of developmental changes in the form and function of manipulation, the contribution of social context to the development of general and specific motor skills, and the development and extent of lateral preference in this species. Complementary studies address the influence of specific individuals and settings on the expression of variable or novel manipulative behaviors. Our understanding of the relationship in humans between early manual activity and later neurobehavioral organization and motor skills will be enhanced if an adequate nonhuman primate model, one opermitting prospective research, is developed in this domain. Evaluation of monkeys for this purpose has not yet occurred. Capuchin monkeys are an attractive choice for exploratory work on the topic of manipulatory development because of their unusual manipulative propensities, including ready use of tools and the significance of socially mediated learning in their acquisition of certain manipulative skills. They are also relatively small-bodied, easy to keep and breed in captivity, and no species in the genus is yet listed as endangered. At the conclusion of this study, comparisons among humans, apes, and this species can be made on several aspects of manipulative development, allowing assessment of capuchins as a nonhuman primate model of human manipulative development.